Stacked sorbent assembly

ABSTRACT

A stacked sorbent assembly for use in sorbent dialysis. The stacked sorbent assembly contains two or more interchangeable sorbent pouches that allow for fluid to freely pass into and through the sorbent materials, while keeping the sorbent materials inside the sorbent pouches. Any of the pouches in the sorbent cartridge can be reused and/or recharged.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/435,772 filed Jun. 10, 2019, which is a continuation of U.S. patentapplication Ser. No. 14/645,394 filed Mar. 11, 2015, which claimsbenefit of and priority to U.S. Provisional Application No. 62/016,611filed Jun. 24, 2014, and the disclosures of each of the above-identifiedapplications are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

The invention relates to an assembly or array of discrete compartmentsof sorbent materials, such as a sorbent pouch, wherein the compartmentscontain at least one sorbent material, and the compartments areconstructed such that fluid freely passes through the compartments whilethe sorbent materials remain inside the compartments.

BACKGROUND

Known dialysate fluid circulation systems and apparatuses have separatehousings wherein a first housing has a sorbent material capable ofperforming a first function such as releasing sodium into dialysatefluid flowing through the first housing, and a second housing has amaterial capable of performing another function such as binding sodiumions from dialysate fluid flowing through the second housing. However,such systems are not modular and customizable and are usually formedinto a single housing design that limits flexibility and the possibilityof customized use personalized to a particular patient. Moreover, suchsorbent systems are one-size-fits-all and operate using similar amountsof sorbent materials across different treatment sessions regardless ofthe unique needs or dialysis parameters for a particular patient. Knownsorbent systems also do not provide for recharging some or all of thecomponents of a sorbent cartridge that would allow reuse of specificcomponents and enable lower long-term costs for operating such systems,nor ease of manufacturing the separate sorbent housings. Providing formultiple sorbent materials within a single sorbent cartridge, or asingle module of a sorbent cartridge, can also be problematic becausefine particles in one of the layers can settle in and intermix into theother layers.

As such, there is a need for a system whereby the individual layers ofsorbent materials within a sorbent cartridge can be kept separate whilemaintaining a unitary sorbent cartridge design. There is also a need forsorbent materials to be reusable or optionally detachable from andre-attachable in a modular and interchangeable design to allow for anyone of disposal, recycling, recharging of sorbent material, orcustomized or personalized use of the sorbent materials. There is also aneed for a sorbent packaging system that can allow dialysate to freelymove into and out of the packaging while keeping the sorbent materialinside the packaging. There is a need for a sorbent packaging made froma porous material that keeps the different sorbent materials separatedfrom each other without requiring additional housings. Similarly, thereis a need for a sorbent cartridge having a separation of materialswithin the sorbent cartridge to allow for isolation of those materials.

There is also a need for a sorbent packaging system, assembly or array,providing for isolation of one or more sorbent materials to allow forcheaper or non-reusable materials to be discarded, while more expensiveand reusable materials are recharged. As such, there is a need for asorbent partition such as a sorbent pouch or a system of sorbent pouchesthat can allow dialysate to freely move into and out of the sorbentpouch while keeping the sorbent material inside. There is a need for asorbent pouch that keeps the different sorbent materials separated fromeach other, but still allows the sorbent materials to be used togetherin a customizable manner. There is also a need for facilitating ease ofpackaging and shipping using a modular interchangeable system to housesorbent materials. There is the need for providing an option forallowing sub-vendors to manufacture sorbent housing or separate assemblyline fill production facilities from one another. There is also a needfor providing a customized sorbent system wherein different layers ofsorbent materials can be used together wherein each sorbent pouch ismodular and interchangeable. There is also a need for reducing finalassembly steps required in preparing a dialysis system for use. Tocombat counterfeiting, there is a need for isolating individual vendorsfrom a sorbent manufacturing process wherein specific sorbent materialsused for dialysis can be pre-filled separately. There is also a need forpre-filling a component housing sorbent materials at precise quantitiesto avoid user error.

SUMMARY OF THE INVENTION

The invention relates to a sorbent assembly. In any embodiment of theinvention, the sorbent assembly can comprise two or more sorbent pouchesstacked in series. The two or more sorbent pouches can be formed from aporous material wherein the sorbent pouches contain at least one sorbentmaterial. The porous material can allow fluid to pass through thesorbent pouches.

In any embodiment of the invention, the porous material can allow fluidto pass through the sorbent pouches but substantially retains the atleast one sorbent material in the sorbent pouches.

In any embodiment of the invention, the porous material can allow fluidto pass through the sorbent pouches but can retain at least 98% byweight of the at least one sorbent material in the sorbent pouches. Inany embodiment of the invention, the porous material can allow fluid topass through the sorbent pouches but can retain anywhere from at least70%, 75%, 80%, 85%, 90%, 92%, 93%, 94%, 95%, 96%, or 97% by weight ofthe at least one sorbent material in the sorbent pouches.

In any embodiment of the invention, any one of the sorbent pouches cancontain sorbent materials selected from the group consisting ofactivated carbon, hydrous zirconium oxide, zirconium phosphate,ion-exchange resin, alumina, urease, and combinations thereof.

In any embodiment of the invention, the sorbent material can be urease,and the porous material can allow fluid containing dissolved urease topass through the sorbent pouches.

In any embodiment of the invention, the sorbent pouches can be attachedto each other via any one of an adhesive, sewn stitch, mechanicalengagement, and combinations thereof.

In any embodiment of the invention, the sorbent pouch can be constructedfrom a porous material selected from any one of bolting cloth, porouspolymer, porous metal, cotton, ashless filter paper, Dacron andpolyethylene terephthalate. In any embodiment of the invention, thesorbent pouch can contain glass beads.

In any embodiment of the invention, the sorbent assembly can comprise atleast one sensor in fluid communication with fluid flowing out from atleast one of the sorbent pouches, the sensor being capable of sensingthe presence and/or concentration of at least one compound in the fluid.

In any embodiment of the invention, at least one sorbent pouch can bereusable.

In any embodiment of the invention, the reusable sorbent pouch cancontain a sorbent material that can be recharged.

In any embodiment of the invention, the reusable sorbent pouch cancontain a sorbent material that is disposable.

In any embodiment of the invention, at least one sorbent pouch can beconstructed of a material that is impregnated with an antimicrobialsubstance and/or anticoagulant.

In any embodiment of the invention, the sorbent assembly can furthercomprise a sorbent assembly shell. The sorbent pouch can have anengagement member capable of cooperatively engaging a groove disposed onan interior surface of the sorbent assembly shell such that in order forthe sorbent pouch to fit into the sorbent assembly shell, the engagementmember is aligned with the groove on the interior wall of the sorbentassembly shell.

In any embodiment of the invention, the at least one sorbent materialscan be separated by a separator.

In any embodiment of the invention, at least one sorbent pouch can havea shape selected from the group comprising a rectangle, a square, adisc, a triangle, an octagon, or a polygon.

In any embodiment of the invention, at least one sorbent pouch can beopened and resealed.

In any embodiment of the invention, at least one sorbent pouch canfurther comprise an o-ring seal member.

In any embodiment of the invention, at least one sorbent pouch cancomprise a double layer of material.

In any embodiment of the invention, at least one sorbent pouch can havea planar base with upwardly extending walls connecting to a planar topwherein the walls can be constructed from a rigid, fluid impermeablematerial.

In any embodiment of the invention, the base and top can be circular andthe upwardly extending walls can slope inward to an axis of the sorbentpouch wherein the top can have a smaller surface area than the base orthe upwardly extending walls can slope outward from the axis of thesorbent pouch wherein the top can have a larger surface area than thebase.

In any embodiment of the invention, the base and top can be rectangular,having four upwardly extending walls sloping inward to an axis of thesorbent pouch wherein the top can have a smaller surface area than thebase or four upwardly extending walls sloping outward from the axiswherein the top has a larger surface area than the base.

In any embodiment of the invention, the top can have an engagementmember disposed upwardly from the top surface of the sorbent pouch.

In any embodiment of the invention, the base can have a receiving groovedisposed on the base for receiving an engagement member.

In any embodiment of the invention, the sorbent pouches can beindividually colored or marked so as to distinguish a sorbent pouchcontaining one sorbent material from a sorbent pouch containing adifferent sorbent material.

In any embodiment of the invention, the coloring or marking cancorrespond to an intended order of sorbent pouches within the sorbentassembly.

In any embodiment of the invention, the planar base of the at least onesorbent pouch can have an engagement member disposed downwardly from abottom surface of the sorbent pouch.

In any embodiment of the invention the planar top of the at least onesorbent pouch can have a receiving groove disposed on a top surface ofthe sorbent pouch for receiving an engagement member.

In any embodiment of the invention, the planar tops of each of thesorbent pouches can have engagement members disposed upwardly from a topsurface of each sorbent pouch, wherein the planar bases of each sorbentpouch can have a receiving groove disposed on a bottom surface of eachsorbent pouch for receiving an engagement member; wherein the sorbentassembly can comprise a sorbent pouch containing urease, a sorbent pouchcontaining zirconium phosphate and optionally at least one sorbent pouchcontaining another sorbent material; and wherein the engagement memberon the planar top of the sorbent pouch containing urease and thereceiving groove on the planar base of the sorbent pouch containingzirconium phosphate can be of a different size than the engagementmember and receiving groove on the at least one sorbent pouch containinganother sorbent material.

In any embodiment of the first invention, the planar bases of each ofthe sorbent pouches can have engagement members disposed downwardly froma bottom surface of each sorbent pouch, wherein the planar tops of eachsorbent pouch can have a receiving groove disposed on a top surface ofeach sorbent pouch for receiving an engagement member; wherein thesorbent assembly can comprise a sorbent pouch containing urease, asorbent pouch containing zirconium phosphate and at least one sorbentpouch containing another sorbent material; and wherein the engagementmember on the planar base of the sorbent pouch containing urease and thereceiving groove on the planar top of the sorbent pouch containingzirconium phosphate can be of a different size than the engagementmember and receiving groove on the at least one sorbent pouch containinganother sorbent material.

In any embodiment of the invention, the sorbent assembly can have atleast one sorbent pouch with urease; wherein the sorbent pouchcontaining urease is constructed of a porous material allowing dissolvedurease to pass through the sorbent pouch.

In any embodiment of the invention, the assembly can have one sorbentpouch that contains alumina and another sorbent pouch that containsurease wherein the sorbent pouch containing urease is constructed of aporous material that allows fluid to pass through the sorbent pouch andalso allows dissolved urease to pass through the sorbent pouch, andwherein the sorbent pouch containing urease is constructed of a porousmaterial that allows fluid and dissolved urease to pass through thesorbent pouch, but substantially retains the alumina. In any embodimentof the invention, the sorbent pouch containing alumina can retain atleast 98% by weight of the alumina.

In any embodiment of the invention, each of the two or more sorbentpouches can comprise sidewalls having a thickness different from thesidewall thicknesses of the other sorbent pouches, such that the two ormore sorbent pouches can have differing interior diameters.

In any embodiment of the invention, each sorbent pouch can have asidewall thickness greater than that of the previous sorbent pouch inseries.

In any embodiment of the invention, each of the two or more sorbentpouches can have differing exterior diameters.

In any embodiment of the invention, each sorbent pouch can have anexterior diameter smaller than that of the previous sorbent pouch inseries.

In any embodiment of the invention, the two or more sorbent pouches caneach contain one or more annular ring. In any embodiment of theinvention, the one or more annular ring can be constructed from a fluidimpermeable substance, and the one or more annular ring can be disposedon the interior circumference of each of the two or more sorbent pouchesand can extend radially into the center of each of the two or moresorbent pouches.

In any embodiment of the invention, the annular ring can have across-sectional shape selected from the group comprising circular,triangular, and rectangular.

Any of the features disclosed as being part of the invention can beincluded in the invention, either alone or in combination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a sorbent cartridge containing sorbentpouches of activated carbon, hydrous zirconium oxide, urease, alumina,and zirconium phosphate.

FIG. 2 perspective view of a sorbent cartridge containing sorbentpouches of activated carbon, hydrous zirconium oxide, urease, alumina,and zirconium phosphate with sensors placed within the sorbent cartridgeto monitor the content of the spent dialysate.

FIG. 3 is a perspective view of two sorbent pouches with the ability toconnect directly together.

FIG. 4 is a top view of a rectangular sorbent pouch.

FIG. 5 is a perspective view of a rectangular sorbent pouch.

FIG. 6 is a top view of a disc-shaped sorbent pouch.

FIG. 7 a is a side view of a string of disc-shaped sorbent pouches.

FIG. 7 b is a top view of a string of disc-shaped sorbent pouches.

FIG. 7 c is a top view of a string of disc-shaped sorbent pouchesshowing the detail of the outer edges of the sorbent pouches.

FIG. 7 d is a perspective view of a string of disc-shaped sorbentpouches showing the detail of the outer edges of the sorbent pouches.

FIG. 8 a is a side view of a string of rectangular sorbent pouches.

FIG. 8 b is a top view of a string of rectangular sorbent pouches.

FIG. 8 c is a top view of a string of rectangular sorbent pouchesshowing the detail of the outer edges of the sorbent pouches.

FIG. 9 a is a perspective view of a sorbent pouch having the ability toopen and reclose via a hinge and a latch member.

FIG. 9 b is a perspective view of a sorbent pouch in an open state.

FIG. 10 a is a perspective view of a sorbent pouch having an internalsealing ring.

FIG. 10 b is a perspective view of a sorbent pouch having an externalsealing ring.

FIG. 11 is a perspective view of a sorbent pouch with an internalseparator.

FIG. 12 a perspective view of a sorbent pouch in a sorbent cartridgewith an o-ring seal member.

FIG. 13 is a perspective view of a sorbent pouch in a sorbent cartridgewith an elastomeric material on the side walls.

FIG. 14 is a perspective view of a sorbent pouch and cartridge withengagement member to ensure correct alignment.

FIG. 15 is a perspective view of a sorbent pouch with a double layer ofmaterial in the center to control flow through the sorbent pouch.

FIG. 16 shows an exploded cross-sectional view of a sorbent cartridgehaving stacked sorbent pouches, with each sorbent pouch in series havinga thicker sidewall, and therefore smaller interior diameter, than thatof the previous sorbent pouch in series.

FIG. 17 shows an exploded perspective view of a sorbent cartridge havingstacked sorbent pouches, with each sorbent pouch in series having athicker sidewall, and therefore smaller interior diameter, than that ofthe previous sorbent pouch

FIG. 18 shows an exploded cross-sectional view of a sorbent cartridgehaving stacked sorbent pouches, with each sorbent pouch in series havinga smaller diameter than that of the previous sorbent pouch.

FIG. 19 shows a cross-sectional perspective view of a sorbent pouchhaving an annular ring disposed on the interior circumference of thesorbent pouch.

DETAILED DESCRIPTION OF THE INVENTION

Unless defined otherwise, all technical and scientific terms used hereingenerally have the same meaning as commonly understood by one ofordinary skill in the relevant art.

The articles “a” and “an” are used herein to refer to one or to morethan one (i.e., to at least one) of the grammatical object of thearticle. By way of example, “an element” means one element or more thanone element.

An “adhesive” is any substance known in the art for use in affixing onesurface to another surface, or to seal two surfaces together.

“Ammonia detector” refers to any apparatus that is capable of detectingthe presence or concentration of ammonia or ammonium ions in a fluid.

An “annular ring” is a ring having a substantially circular shape. Thecross-section of the ring may be rectangular, triangular, round, or anyother known shape. The ring may be constructed of any rigid orsemi-rigid material, and may be adhered to the inner surface of asorbent pouch by any means known in the art. An annular ring may also bean “o-ring.”

An “axis of the sorbent pouch” describes an imaginary line runningvertically down the center of the sorbent pouch, situated in the centerof the surface of the sorbent pouch when viewed from the topperspective.

The term “cartridge” refers to any container designed to contain apowder, fluid, or gas made for ready connection to a device, structure,system, flow path or mechanism. The container can have one or morecompartments. Instead of compartments, the container can also becomprised of a system of two or more modules connected together to formthe cartridge wherein the two or more modules once formed can beconnected to a device, structure, system, flow path or mechanism.

A “circular shape” describes a sorbent pouch constructed in a generallyround shape having the form of a circle. This term is not intended tolimit the shape of the sorbent pouch to any particular size ordimensions, and may encompass oval or oblong configurations as well.

A “compartment” means a part or a space designated, defined, marked orpartitioned off from a structure. For example, a urease compartment in asorbent cartridge is a space defined within the sorbent cartridgecontaining urease, including urease immobilized to an immobilizingsorbent material, such as alumina. Optionally, the compartment can be inselected fluid communication with other compartments or modules of thesorbent system. The compartment can be physically separated or markedoff without a physical barrier.

The term “comprising” includes, but is not limited to, whatever followsthe word “comprising.” Thus, use of the term indicates that the listedelements are required or mandatory but that other elements are optionaland may or may not be present.

The term “consisting of” includes and is limited to whatever follows thephrase “consisting of.” Thus, the phrase indicates that the limitedelements are required or mandatory and that no other elements may bepresent. The term “consisting essentially of” includes whatever followsthe term “consisting essentially of” and additional elements,structures, acts or features that do not affect the basic operation ofthe apparatus, structure or method described.

The term “detachable” or “detached” relates to any component of thepresent invention that can be separated from a system, module, sorbentpouch, cartridge or any component of the invention. “Detachable” canalso refer to a component that can be taken out of a larger system withminimal time or effort. In certain instances, the components can bedetached with minimal time or effort, but in other instances can requireadditional effort. The detached component can be optionally reattachedto the system, module, cartridge or other component. A detachable modulecan often be part of a reusable module.

“Dialysate” is the fluid that passes through the dialyzer on the side ofthe dialysis membrane that is opposite to the fluid (e.g. blood) that isbeing dialyzed.

A “disc-like shape” describes a sorbent pouch forming a flat, circularshape, as in a compressed cylinder. This definition is not intended tolimit the dimensions or radius of the sorbent pouch, and may thereforeencompass discs having an oval shape, and discs of any radial width orthickness.

“Disposable” refers to a component that is to be removed from the systemand not reused.

A “double layer of material” describes a second layer of material of thesame or smaller area than the primary layer of material, disposed on thesurface of the primary layer of material forming a surface of a sorbentpouch. The material used to form the double layer can be the same ordifferent from the material forming the primary layer. Any rigid orflexible porous material known in the art is contemplated.

An “elastomer” or “elastomeric material” is a material comprising apolymer having high elasticity, such that the material may be easilystretched and shaped to be adapted to an internal cavity defined by asorbent cartridge.

“Engagement members” allow compartments to cooperatively engage. Incertain embodiments, these engagement members may be clasps or latches.In one embodiment, an engagement member allows for coupling of a topportion and a bottom portion of a sorbent pouch that can be opened andresealed.

“Flow” refers to the movement of a fluid or gas.

A “fluid” is a liquid substance optionally having a combination of gasand liquid phases in the fluid. Notably, a liquid, as used herein, cantherefore also have a mixture of gas and liquid phases of matter.

The term “fluid communication” refers to the ability of fluid or gas tomove from one component or compartment to another within a system or thestate of being connected, such that fluid or gas can move by pressuredifferences from one portion that is connected to another portion.

A “fluid impermeable material” is any material through which fluidcannot pass.

The term “fluidly connectable” refers to the ability of providing forthe passage of fluid or gas from one point to another point. The twopoints can be within or between any one or more of compartments,modules, systems, components, and rechargers, all of any type.

A “geometric shape” refers any geometric shape in Euclidean and othergeometries such as a rectangle, disc, triangle, or polygon inter alia.In reference to a sorbent pouch as described in the invention, thegeometric shape can refer to one or more side of the sorbent pouchwherein a rectangular sorbent pouch can be generally constructed to havea rectangular shape at least on one side to form a porous sealed bag.

“Immobilized,” as used to refer to a chemical component, refers to aconfiguration wherein a chemical component is held in place by someforce. The force may be provided by absorption, adsorption, adhesion, orany other method for the chemical to be held in place.

The term “immobilizing sorbent material” refers to the process of asorbent material being placed onto another material, such that thesorbent material is held in place by some force. The force may beprovided by absorption, adsorption, adhesion, or any other method forthe chemical to be held in place.

The term “impregnated” describes any process known to a person ofordinary skill in the art by which a material may be caused to absorb orbe saturated with a substance. In one embodiment, the material forming asorbent pouch may be impregnated with an anticoagulant, such that thesurface of the sorbent pouch absorbs the anticoagulant.

The term “in-part” describes a portion up to and including one hundredpercent. For example, a component formed in-part by a material meansthat the material forms at least some portion of the component, and thatthe material may form up to the entire component.

“Mechanical engagement” describes any means known in the art ofphysically attaching two components together, for example by use of alatch and flange, or male and female interlocking components.

“Module” refers to a discreet component of a system. Each of the modulescan be fitted to each other to form a system of two or more modules.Once fitted together, the modules can be in fluid connection and resistinadvertent disconnection. A single module can represent a cartridge tobe fitted to a device or mechanism if the module is designed to containall the necessary components for an intended purpose such as a sorbentfor use in dialysis. In such a case, the module can be comprised of oneor more compartments within the module. Alternatively, two or moremodules can form a cartridge to be fitted to a device or mechanism whereeach module individually carries separate components but only whenconnected together contain in summation all the necessary components foran intended purpose such as a sorbent for use in dialysis. A module canbe referred to as a “first module,” “second module,” “third module,”etc. to refer to any number of modules. It will be understood that thedesignation of “first,” “second,” “third,” etc. does not refer to therespective placement of the module in the direction of fluid or gasflow, and merely serves to distinguish one module from another unlessotherwise indicated.

The term “non-reusable” refers to a component that cannot be reused inthe component's current state. In certain instances, the termnon-reusable can include the concept of being disposable, but is notnecessarily limited to just being disposable.

An “o-ring seal member” is a mechanical gasket having a ring shape; itis a loop of elastomer or other suitable material known in the art witha round cross-section, designed to be seated in a groove and compressedduring assembly between two or more parts, creating a seal at theinterface. In one embodiment, an o-ring seal member may be used to sealthe interface between a sorbent pouch and a sorbent cartridge such thatfluid is directed through, rather than around, the sorbent pouch.

The terms “pathway,” “conveyance pathway,” “fluid flow path,” and “flowpath” refer to the route through which a fluid or gas, such as dialysateor blood, travels.

A “planar top” or “planar base” is a surface perpendicular to the axisof the urease pouch culminating at the uppermost portion of the upwardlyextending walls of a urease pouch, or a flat surface culminating at thebottommost portion of the downwardly extending walls of a urease pouch,respectively. The planar top may be any geometric shape and dimensionscomplementary to the upwardly extending walls of the urease pouch, forexample round, square, triangular or rectangular. A circular planar topor planar base is a flat surface having a circular shape, while arectangular planar top or planar base is a flat surface having a squareor rectangular shape.

A “porous material” may describe any suitable porous material known inthe art from which a sorbent pouch may be constructed. For example, theporous material can include, but is not limited to, bolting cloth,porous polymer, porous metal, cotton, ashless filter paper, Dacron andpolyethylene terephthalate. The porous material chosen for individualsorbent pouches may be selected based upon specific porosity in view ofthe sorbent material to be contained within the sorbent pouch.

A “porous structure” describes a sorbent pouch being formed of a porousmaterial, wherein the sorbent pouch can be manipulated to fit aninternal cavity defined by a sorbent cartridge.

“Recharging” refers to the process of treating spent sorbent material torestore the functional capacity of the sorbent material, so as to putthe sorbent material back into a condition for reuse or for use in a newdialysis session. In some instances, the total mass, weight and/oramount of “rechargeable” sorbent materials remain the same. In otherembodiments, the total mass, weight and/or amount of “rechargeable”sorbent materials may change. Without being limited to any one theory ofinvention, the recharging process may involve exchanging ions bound tothe sorbent material with different ions, which in some instances mayincrease or decrease the total mass of the system. However, the totalamount of the sorbent material will in some instances be unchanged bythe recharging process. Upon a sorbent material undergoing “recharging,”the sorbent material can then be said to be “recharged.” Recharging ofrechargeable sorbent materials is not the same as replenishing of aparticular sorbent material such as urease.

“Reusable” refers in one instance to a material that can be used morethan one time, possibly with treatment or recharging of the materialbetween uses. Reusable may also refer to a cartridge that contains amaterial that can be recharged by recharging the material(s) containedwithin the cartridge.

A “rigid structure” describes a sorbent pouch being formed of inflexiblematerial such that the sorbent pouch cannot be manipulated and reshapedto be adapted to an internal cavity defined by a sorbent cartridge, butinstead maintains its shape.

A “semi-rigid structure” describes a sorbent pouch having surfaces thatcan be flexed, but that are substantially rigid unless force is appliedto cause the surfaces to flex.

A “sensor” is a component capable of determining the states of one ormore variables in a system. In one embodiment, a sensor may be capableof sensing the presence and/or concentration of at least one compound inthe fluid flowing through at least one sorbent pouch, using any meansknown in the art.

A “separator” is a layer of flexible or rigid material positioned withina sorbent pouch that divides the sorbent pouch into top and bottomportions, such that sorbent materials housed in the top and bottomportions, respectively, do not come in contact with each other. Theseparator is formed of a porous material such that spent dialysate orother fluid may flow between the top and bottom portions of the sorbentpouch through the separator, but such that the sorbent materials housedin the top and bottom portions of the sorbent pouch cannot pass throughthe separator.

A “sorbent assembly shell” is an empty sorbent cartridge housing intowhich the stacked sorbent assembly is inserted.

“Sorbent cartridge” refers to a cartridge that can contain one or moresorbent materials. The cartridge can be connected to a dialysis flowpath. The sorbent materials in the sorbent cartridge are used forremoving specific solutes from solution, such as urea. The sorbentcartridge can have a single compartmental design wherein all sorbentmaterials necessary for performing dialysis are contained within thesingle compartment. Alternatively, the sorbent cartridge can have amodular design wherein the sorbent materials are dispersed across atleast two different modules, which can be connected to form a unitarybody. Once the at least two modules are connected together, theconnected modules can be referred to as a sorbent cartridge, which canbe fitted to a device or mechanism. When a single module contains allthe sorbent materials necessary for performing dialysis, the singlemodule can be referred to as a sorbent cartridge.

“Sorbent materials” are materials capable of removing specific solutesfrom solution, such as urea or urea byproducts.

The term “sorbent pouch” refers to a structure that contains at leastone sorbent material, and is constructed from a material that can allowfluid to freely pass through the sorbent pouch while substantiallyretaining the sorbent material inside the pouch.

A “sewn stitch” is a method of sealing two surfaces together using aneedle and a thread composed of any material known in the art.

“Spent dialysate” is a dialysate contacted with blood through a dialysismembrane and contains one or more impurities, or waste species, or wastesubstance, such as urea.

A “square” or “rectangular” shape describes a sorbent pouch having fouredges and four angles. This description is not intended to limit thesize and dimensions of the sorbent pouch, and may therefore encompasssorbent pouches having corners with angles greater than or less thanninety degrees, and with edges of differing lengths with respect to eachother.

The term “substantially,” is used in conjunction with a term to describea particular characteristic. For example, as used in the phrase“substantially retains the at least one sorbent material in the sorbentpouches,” the term describes the ability to retain a sorbent material orparticles characterized by an average pore diameter such that asignificant amount of the material or particles are retained within thesorbent pouch.

A “threaded fitting” is a fitting for connecting two components whereinthe male portion has a helical ridge wrapped around a cylinder, and thefemale portion is a cylindrical hole with internal helical ridges sothat when the male portion is screwed into the female portion the twocomponents are locked together.

A “triangular shape” describes a sorbent pouch having three edges andthree corners, wherein the edges and corners may vary in length anddegree individually and with respect to each other.

A “twist-lock fitting” is a fitting for connecting two componentswherein the male portion of the fitting contains a head with a lengthexceeding its width, the female portion of the fitting is a hole with alength that exceeds its width and is larger than the male portion, sothat when the male portion is inserted into the female portion andeither portion is twisted the two components become locked together.

“Upwardly extending walls” describe the surfaces extending radiallyoutward from the top and bottom surfaces of a sorbent pouch. Forexample, in a sorbent pouch having a disc-like shape, the circular topand bottom portions of the sorbent pouch are connected by the roundedupwardly extending wall of the sorbent pouch. The upwardly extendingwalls may be of any shape or dimensions complementary to thecorresponding top and bottom portions of the sorbent pouch. In the caseof a triangular shaped sorbent pouch, the upwardly extending walls wouldextend from a bottom portion of the sorbent pouch and culminate at avertex, in the absence of a top portion.

Stacked Sorbent Assembly

This invention is drawn to a sorbent cartridge comprising a stackedassembly of sorbent pouches. One non-limiting embodiment of theinvention is shown in FIG. 1 . The sorbent cartridge 201 can comprise asorbent pouch containing activated carbon 202, a sorbent pouchcontaining hydrous zirconium oxide 203, a sorbent pouch containingalumina/urease 204, and a sorbent pouch containing zirconium phosphate205. In any embodiment of the invention, the alumina and urease canoccupy separate sorbent pouches (not shown). Spent dialysate can enterthrough the bottom surface 207 of the sorbent cartridge 201, and flowthrough each of the sorbent pouches 202-205 sequentially, and then flowout of the sorbent cartridge 201 through the top surface 206 of thesorbent cartridge 201. In this way, the spent dialysate can come intocontact with each sorbent material layer, while each sorbent materiallayer is kept separate from each of the other layers. One skilled in theart will understand that, in any embodiment of the invention, thesorbent pouches may be arranged in alternate orders and still be withinthe scope of the invention. For example, the first sorbent pouch 202 maycontain activated carbon, the second sorbent pouch 203 may containalumina/urease, the third sorbent pouch 204 may contain hydrouszirconium oxide, and the fourth sorbent pouch 205 may contain zirconiumphosphate. In any embodiment of the invention, the first sorbent pouch202 may contain activated carbon, the second sorbent pouch 203 maycontain alumina/urease, the third sorbent pouch 204 may containzirconium phosphate and the fourth sorbent pouch 205 may contain hydrouszirconium oxide. The precise order of the sorbent pouches within thesorbent cartridge 201 is not critical to the invention so long as asorbent pouch containing zirconium phosphate is located downstream ofthe sorbent pouch containing alumina/urease. In any embodiment of theinvention, a sorbent pouch can contain multiple sorbent materials,either arranged in layers or alternatively intermixed within the sorbentpouch. In any sorbent pouch, glass beads can be incorporated into thesorbent material to facilitate flow. Additionally, any number of sorbentpouches arranged sequentially in the sorbent cartridge is envisioned.

In any embodiment of the invention, sensors may be positioned after orbetween the sorbent pouches and optionally inside a sorbent cartridgehousing the sorbent pouches, to ensure that fluid is properly passingthrough the sorbent pouch and that the sorbent material within thesorbent pouch is properly removing or converting the toxins present inthe spent dialysate. For example, as shown in FIG. 2 , a sorbentcartridge 291 can comprise a sorbent pouch containing activated carbon292, a sorbent pouch containing hydrous zirconium oxide 293, a sorbentpouch containing alumina/urease 294, and a sorbent pouch containingzirconium phosphate 295. The sorbent pouches can be placed in any order,so long as the sorbent pouch containing zirconium phosphate is locateddownstream of the sorbent pouch containing alumina/urease. In anyembodiment of the invention, the alumina and urease can occupy separatesorbent pouches (not shown). For example, the first sorbent pouch 292can contain activated carbon, the second sorbent pouch 293 can containalumina/urease, the third sorbent pouch 294 can contain hydrouszirconium oxide and the fourth sorbent pouch 295 can contain zirconiumphosphate. In any embodiment of the invention, the first sorbent pouch292 can contain alumina/urease, the second sorbent pouch 293 can containhydrous zirconium oxide, the third sorbent pouch 294 can containzirconium phosphate and the fourth sorbent pouch 295 can containactivated carbon. Further, any sorbent pouch can contain multiplesorbent materials, either arranged in layers or intermixed as describedabove, thus allowing for the use of less sorbent pouches. A sensor 296can be placed after the sorbent pouch containing activated carbon 292 totest the spent dialysate for toxins that are normally removed byactivated carbon, such as β-2 microglobulin or creatinine. Anothersensor 297 can be deployed after the sorbent pouch containing hydrouszirconium oxide 293 to test the spent dialysate for the presence ofphosphates or fluoride ions. A third sensor 298 can be deployed afterthe alumina/urease containing sorbent pouch 294 to test for the presenceof urea. A fourth sensor 299 can be deployed after the zirconiumphosphate containing sorbent pouch 295 to test for the presence ofammonia. Although FIG. 2 shows four sensors being used, the presentinvention contemplates using any number of sensors, including more orless than four. The presence of additional compounds that may be presentin spent dialysate can be tested, and the presence of all of thecompounds described above need not be tested. In any embodiment of theinvention, the sensors can be conductivity sensors.

In any embodiment of the invention, the sorbent pouches may be made withfluid impermeable side walls. The side walls may be made out of metal orany other material known in the art, such as plastic. In any embodimentof the invention where the top and bottom layers of the sorbent pouchesare made out of a fluid permeable substance, such as fabric, the sidewalls of the sorbent pouches may be made out of a fluid impermeablesubstance. In any embodiment of the invention, the sorbent pouchesthemselves may connect together directly, eliminating the need for anexternal housing. In any embodiment of the invention, the sorbentpouches themselves can form the sorbent cartridge. In any embodiment ofthe invention, shown in FIG. 3 , the top and bottom layers of thesorbent pouch can have a means for connecting to another sorbent pouch.For example, first sorbent pouch 301 can have engagement members 303 onthe top surface of the sorbent pouch 301. Second sorbent pouch 302 canhave engagement members 304 on the bottom surface of the sorbent pouch302. Engagement members 303 of the first sorbent pouch 301 andengagement members 304 of the second sorbent pouch 302 can connecttogether in any known fashion to seal the two sorbent pouches together.O-ring 305 on the first sorbent pouch 301 and o-ring 306 on the secondsorbent pouch 302 can create a water-tight seal when the two sorbentpouches are connected, eliminating any leaks from the interface. Becausethe side wall 307 of the first sorbent pouch 301 and the side wall 308of the second sorbent pouch 302 are impermeable to fluid, there will beno leakage from the sides of the structure either. In this way, thesorbent pouches of the invention can fit together without the need forcontainment in an external sorbent cartridge.

The engagement members 303 and 304 can be constructed in any knownfashion to create a sealed structure. In FIG. 3 , they are shown as atwist lock fitting. The engagement members 303 can fit into the holesserving as engagement members 304. When the sorbent pouches are twisted,the engagement members 303 can turn relative to the holes 304. Thiscreates a construct wherein the top portion of engagement members 303cannot fit back out of the holes 304. In order to separate the sorbentpouches, one must twist the sorbent pouches back in the oppositedirection so that the tops of engagement members 303 can once again fitthrough the holes 304 and allow easy disengagement. Any other knownmethod of connecting the first sorbent pouch 301 and the second sorbentpouch 302 is contemplated by this invention.

First sorbent pouch 301 can also have engagement members similar to 304disposed on the bottom surface of the sorbent pouch (not shown) tofacilitate the attachment of another sorbent pouch before the firstsorbent pouch 301. Similarly, second sorbent pouch 302 can haveengagement members similar to 303 disposed on the top surface of thesorbent pouch (not shown) to facilitate the attachment of anothersorbent pouch after the second sorbent pouch 302.

In any embodiment of the invention, the engagement members can beconfigured so as to ensure proper sequencing of the sorbent pouches. Forexample, a zirconium phosphate sorbent pouch must be placed downstreamof a sorbent pouch containing urease to remove the ammonia created bythe breakdown of urea in the urease sorbent pouch. The engagementmembers on the bottom of the zirconium phosphate sorbent pouch and thetop of the urease sorbent pouch may be configured so that they can onlyengage with one another; that is so that the zirconium phosphate sorbentpouch can only be attached immediately downstream of the urease sorbentpouch and the urease sorbent pouch can only be attached immediatelyupstream from the zirconium phosphate sorbent pouch. In any embodimentof the invention, this can be accomplished by using engagement membersfor the top surface of the urease sorbent pouch and the bottom surfaceof the zirconium phosphate sorbent pouch that are of a different sizethan the engagement members on other sorbent pouches. Alternatively, theindividual sorbent pouches may be colored, or marked, to indicate theproper sequencing of sorbent pouches.

In any embodiment of the invention, two or more sorbent pouchescontaining the same sorbent material can be used. For highly uremic orparticularly large patients, more of a given sorbent material may benecessary. In such cases, a second sorbent pouch containing, forexample, zirconium phosphate, may be used in the system. This would givethe patient twice as much of the sorbent material, allowing the removalof a greater amount of a given toxin or toxins in a single uninterrupteddialysis session.

The stacked assembly of the invention utilizes separate sorbent pouchesthat contain individual portions of sorbent material, or multiple layersof sorbent material. The sorbent pouches are designed such that spentdialysate or water may pass through the sorbent pouch and into thesorbent material or materials within, and the spent dialysate or watermay then pass out of the sorbent pouch, while the sorbent materialsremain inside the sorbent pouch.

The sorbent pouches of the invention can be constructed in any shape.For convenience, they are often drawn as circular or disc shaped.However, any of the described embodiments of the invention can be madein any shape, including triangular, rectangular, etc.

For example, FIGS. 4 and 5 show a rectangular-shaped sorbent pouch 41,whereas FIG. 6 shows a disc shaped sorbent pouch. The sorbent pouchesmay be constructed of any known material including bolting cloth, porouspolymer, porous metal, cotton, ashless filter paper, Dacron, andpolyethylene terephthalate as described herein, and each may beconstructed in any shape.

In any embodiment of the invention, the sorbent pouches can beconfigured as shown in FIG. 4 . The sorbent pouch 41 can be constructedof a material that can allow fluid to pass through the sorbent pouch 41,but will not allow the sorbent material 42 contained within the sorbentpouch 41 to pass out of the sorbent pouch 41. The sorbent material 42can be placed loosely in the sorbent pouch 41, allowing the sorbentmaterial 42 to move within the sorbent pouch 41, but not to travel outof the sorbent pouch 41. The sorbent pouch 41 can be made in any size orshape.

FIG. 5 shows a rectangular sorbent pouch embodiment in which the sorbentmaterial is contained in a raised inner portion of the sorbent pouch 51,while the outer perimeter of the sorbent pouch, having a serrated edge52, is sealed by any means known in the art, including heat or pressurestamping, sewing, or adhesive sealing. The serrated edge 52 of thesorbent pouch may be permanently sealed, or may alternatively beresealable, such that the sorbent pouch may be opened and reclosed. Forexample, the serrated edge 52 may be sealed with a resealable adhesive,hook and loop fasteners (not shown), or with interlocking ridges (notshown) that may be separated and reclosed by the user. Optionally, alatch member (not shown) may be included on the serrated edge 52 of thesorbent pouch 51 to provide additional strength in sealing the sorbentpouch 51. In any embodiment of the invention, the outer edge may simplybe a folded edge. In use, compression from the other materials within asorbent cartridge can keep the folded edge sealed and the sorbentmaterials inside the sorbent pouch 51. In any embodiment of theinvention, the sorbent pouch 51 may be sealed with drawstrings that whentightened create a seal.

In any embodiment of the invention, the sorbent pouch can be formed froma porous material that allows fluid to pass through the sorbent poucheswherein substantially all of the sorbent material or particles areretained by the porous material. Sorbent materials are generally formedfrom a solid substance that adsorbs and/or absorbs other substances. Inany embodiment of the invention, the porous material can allow fluid topass through the sorbent pouches but substantially retains the sorbentmaterial in the sorbent pouch. In any embodiment of the invention, theporous material can allow fluid to pass through the sorbent pouches butretain at least 98% by weight of one sorbent material in the sorbentpouch. In any embodiment of the invention, the porous material can allowfluid to pass through the sorbent pouches but can retain anywhere fromat least 70%, 75%, 80%, 85%, 90%, 92%, 93%, 94%, 95%, 96%, or 97% byweight of one sorbent material in the sorbent pouch.

In any embodiment of the invention, the pore size of one or more of thesorbent pouches may be large enough so that the sorbent material canleave the sorbent pouch. For example, a sorbent pouch containing solidurease may be made with a pore size large enough to allow the urease totravel out of the sorbent pouch. The urease in any embodiment of theinvention can be dissolved by the fluid as it passes through the sorbentpouch during priming of the sorbent cartridge prior to dialysis, and theurease can exit the sorbent pouch. The urease in solution can thencontact a sorbent pouch containing immobilized alumina, where the ureasewill become bound to the alumina in the alumina sorbent pouch.Alternatively, the sorbent cartridge can contain a sorbent pouchcontaining alumina, and a solution of urease can be injected into theflow path before the sorbent cartridge. The urease solution can enterthe sorbent pouch containing alumina, where the urease will become boundto the alumina in the alumina sorbent pouch.

However, in any embodiment of the invention, it may be desirable toretain the dissolved urease in the sorbent pouch and as such the sorbentpouch is constructed from a material that substantially retains theurease within the sorbent pouch. In any embodiment of the invention, thesorbent assembly can comprise two or more sorbent pouches stacked inseries.

The size of the sorbent pouches is flexible. Because different amountsof each sorbent material may be required for a dialysis session, thesorbent pouches of the present invention may be in multiple sizes. Inany sorbent pouch, glass beads can be incorporated into the sorbentmaterial to facilitate flow.

The sorbent pouches may be constructed of a flexible or rigid porousmaterial. The porous material can be selected from any non-toxicmaterial suitable for the intended use in a dialysis wherein thematerial can allow fluid to pass through the material yet substantiallyretains the sorbent material in the sorbent pouch. The porous materialcan be selected from the materials having the appropriate porosity,strength and durability. In any embodiment of the invention, theflexible material can allow fluid to pass through the sorbent pouchesbut can retain at least 98% by weight of one sorbent material in thesorbent pouch. In any embodiment of the invention, the porous materialcan allow fluid to pass through the sorbent pouches but can retainanywhere from at least 70%, 75%, 80%, 85%, 90%, 92%, 93%, 94%, 95%, 96%,or 97% by weight of one sorbent material in the sorbent pouch. When thematerial is selected for use with urease, alumina may also be providedin the sorbent pouch. Because the alumina will adsorb the urease, andkeep the urease from flowing out of the sorbent pouch, the porousmaterial need only substantially retain the alumina.

In any embodiment of the invention, the sorbent pouches may beconstructed out of both a flexible and a rigid material. For example,the top and bottom of the sorbent pouch may be constructed from aflexible material, while the sides of the sorbent pouch may beconstructed from a rigid material. In any embodiment of the invention,the sorbent pouches can be made out of a material such as a porouspolymer. The polymer may be made porous by creating small holes or poresin an otherwise solid polymer material. The polymer may be constructedfrom polyethylene terephthalate, high density polyethylene, low densitypolyethylene, polyvinyl chloride, polypropylene, polystyrene, or anyother polymer known in the art. In any embodiment of the invention wherethe sorbent pouch is made of fabric, the weave of the fabric can have aspecified porosity suitable for use with the sorbent material describedherein for the intended use of dialysis. The pores of the sorbent pouchmaterial must be large enough to allow the spent dialysate to freelytravel into and out of the sorbent pouch, while at the same time must besmall enough to keep the particles of the sorbent material inside thesorbent pouch. For this reason, sorbent pouches with different pore ormesh sizes can be utilized for different material layers. In anyembodiment of the invention, the sorbent pouch may be made out of anatural fiber, such as cotton. In any embodiment of the invention, thesorbent pouch may be constructed from ashless filter paper. The sorbentpouches may also be constructed out of a synthetic material such asDacron, or polyethylene terephthalate.

In any embodiment of the invention, multiple sorbent pouches may beconnected as a string of sorbent pouches, as shown in FIGS. 7 a, 7 b, 7c, 7 d, 8 a, 8 b and 8 c . The individual sorbent pouches 311-315 in thecase of disc shaped sorbent pouches, and 321-325 in the case ofrectangular sorbent pouches, may be permanently or separably connectedat their outer edges 316-320 in the case of disc shaped sorbent pouchesor 326-330 in the case of rectangular sorbent pouches, by any meansknown in the art, including by perforations in the material forming theouter edges 316-320 or 326-330. The individual sorbent pouchescomprising the string of sorbent pouches may be composed of the samematerial; may be composed of different materials such that each sorbentpouch in the string of sorbent pouches is composed of a differentmaterial; or may be composed of different materials such that somesorbent pouches in the string of sorbent pouches are composed of thesame material, while others are composed of differing materials, and arearranged in a random or repeating pattern. The materials of which theindividual sorbent pouches are composed may be selected withparticularity to the sorbent material housed inside the sorbent pouch.For example, sorbent pouches containing activated carbon may require alarger mesh to prevent the larger particles from escaping the sorbentpouch. By contrast, sorbent pouches containing hydrous zirconium oxidemay require a smaller mesh to prevent the smaller particles fromescaping the sorbent pouch. Any combination of sorbent pouch materialsand mesh sizes among the string of sorbent pouches, and any number ofindividual sorbent pouches making up the string of sorbent pouches, isenvisioned. Additionally, the sorbent pouches may be constructed in anyshape, including but not limited to, rectangular or circular.

In any embodiment of the invention, the sorbent pouches of the presentinvention may be designed so that they can be opened, as shown in FIGS.9 a and 9 b . Top portion 213 of the sorbent pouch 211 and bottomportion 214 of the sorbent pouch 211 may be connected by a hinge 216 anda latch member 212. When latch member 212 on the top portion 213 ofsorbent pouch 211 is engaged with flange 215 on bottom portion 214 ofthe sorbent pouch 211, the top portion 213 of the sorbent pouch 211 canbe firmly sealed to the bottom portion 214 of the sorbent pouch 211.When latch member 212 of the sorbent pouch 211 is disengaged from flange215, top portion 213 can pivot on hinge 216 to separate from bottomportion 214. The sorbent material (not shown) within the sorbent pouch211 can then be removed in order to be discarded or recharged. Thesorbent pouch 211 itself may be reused. The sorbent pouch 211 can beclosed as shown in FIG. 9 b by pivoting the top portion 213 of thesorbent pouch 211 so that top portion 213 and bottom portion 214 meet,and reengaging latch member 212 on the top portion 213 of the sorbentpouch 211 with flange 215 on the bottom portion 214 of the sorbent pouch211. Any type of connection between the top portion 213 and bottomportion 214 of the sorbent pouch 211 is contemplated by this invention.For example, the top portion of the sorbent pouch may include multiplelatches in the absence of a hinge member (not shown), while the bottomportion of the sorbent pouch can include engagement members. When thetop portion is placed onto the bottom portion and twisted, the latchescan engage the engagement members, creating a connection that can beresistant to inadvertent opening. In order for the connection to bebroken, the top portion of the sorbent pouch can be twisted in theopposite direction, allowing the two portions to separate.

In any embodiment of the invention, the sorbent pouches may beconstructed so that they cannot easily be opened. In any embodiment ofthe invention, the sorbent pouches can be completely sealed to form acomplete enclosure around the sorbent material. During construction ofthe sorbent pouch, once the sorbent material is added, the sorbent pouchcan be sealed by any possible means. The sorbent pouches can be heatsealed to fuse the edges of the sorbent pouch together. In anyembodiment of the invention, an adhesive may be used to connect theedges together. In any embodiment of the invention where a fiber is usedto construct the sorbent pouches, the edges may be sewn or woventogether to create a sealed sorbent pouch. Any type of chemical ormechanical closure to form the sorbent pouches is contemplated by thisinvention.

In any embodiment of the invention, as shown in FIGS. 10 a and 10 b ,the sorbent pouches may have an interior or exterior ring 225 disposedinside of or around the sorbent pouch 221, respectively, creating anadditional sealing member to secure the top portion 223 of the sorbentpouch 221 to the bottom portion 224 of the sorbent pouch 221. Thecoupled surfaces of the rings may be coated in an adhesive material, orthe rings may be attached by any other known coupling means. In anyembodiment of the invention, the rings may be welded. In any embodimentof the invention, the rings may be mechanically attached to the sorbentpouches such as with rivets, screws or clamps. In any embodiment of theinvention, engagement hooks may be placed on the rings (not shown),wherein the engagement hooks can attach to the sorbent pouch in asimilar fashion as described for connecting the top and bottom portionsof the sorbent pouches in FIGS. 9 a and 9 b.

In any embodiment of the invention, such as that shown in FIG. 11 , asingle sorbent pouch can contain multiple sorbent materials. Sorbentpouch 241 can comprise a separator 244 within the sorbent pouch. Theseparator 244 can run through the entire interior space of the sorbentpouch 241. The separator 244 creates, within the sorbent pouch 241, atop portion 242 and a bottom portion 243, which are kept completelyseparate from each other. One sorbent material may be placed in the topportion 242 of the sorbent pouch 241, and a different sorbent materialmay be placed in the bottom portion 243 of the sorbent pouch 241. Thisallows two different materials to be placed within a single sorbentpouch, but remain separate from one another. In any embodiment of theinvention, two or more sorbent materials can be placed in a singlesorbent pouch without a separator. The sorbent materials may be arrangedin layers within the sorbent pouch, or may be intermixed. The separator244 can be constructed from the same material as the sorbent pouch 241itself, or may be a different material that still allows fluid to passthrough the separator 244 freely, while preventing passage of thesorbent material.

In any embodiment of the invention, more than one separator can be usedwithin a single sorbent pouch. The present invention contemplatessorbent pouches containing 2, 3, 4 or more separators within a singlesorbent pouch.

In any embodiment of the invention, multiple sorbent materials can bemixed within a sorbent pouch. Mixing different sorbent materialstogether can be accomplished without a loss in efficiency of the sorbentmaterials.

The sorbent pouches of the present invention can have a mechanism tocreate a seal between the sorbent pouch and the inner surface of thesorbent cartridge in which the sorbent pouch is placed, such that fluidis kept from flowing around the sorbent pouch and instead is directedinto the sorbent pouch. FIG. 12 shows one non-limiting embodiment of aseal mechanism. A flexible sorbent pouch 251, such as one made out of afiber, can be placed inside of a sorbent cartridge 252. In anyembodiment of the invention, the sorbent pouch may be made out of arigid material, such as a polymer or metal. In order to avoid asituation in which spent dialysate flows around the sorbent pouch 251and therefore does not contact the sorbent material inside the sorbentpouch 251, the sorbent pouch 251 may be sealed to the interior surfaceof the sorbent cartridge 252. O-ring 253 placed on the circumference ofsorbent pouch 251 can form a seal with the sorbent cartridge 252 so asto prevent spent dialysate from flowing around the sorbent pouch 251,and instead through the sorbent pouch 251. The sorbent pouch 251 may befilled so that the circumference of the sorbent pouch 251 is slightlywider than that of the sorbent cartridge 252. This will ensure that thesorbent pouch 251 covers the entire inner area of the sorbent cartridge252 and that there are no spaces for fluid to pass by without flowingthrough the sorbent pouch 251. O-ring 253 can also serve to ensure thatsorbent pouch 251 keeps the intended shape by providing a semi-rigidborder.

In any embodiment of the invention, as shown in FIG. 13 , an elastomericmaterial 263 may be disposed on the edges of the sorbent pouch 261. Whenthe sorbent pouch 261 is placed in the sorbent cartridge 262, theelastomeric material 263 functions like the o-ring described above tocreate a seal and keep liquid from flowing around the sorbent pouch 261.The elastomeric material 263 can be made to completely cover the outsideedges of the sorbent pouch 261, or the elastomeric material can bedisposed in one or more thin strips of material. In any embodiment ofthe invention, the inside walls of the sorbent cartridge 262 may becoated in an elastomeric substance (not shown), which will function toform the same seal when a rigid or semi-rigid sorbent pouch is placedwithin. In any embodiment of the invention, the sorbent pouches may beconstructed to be slightly larger than the sorbent cartridge. When theuser inserts the sorbent pouches into the sorbent cartridge, the sorbentpouch can be compressed slightly to fit in the sorbent cartridge. Thiswill ensure that the sorbent pouches cover the entire area inside thesorbent cartridge and facilitate the formation of a seal around theedges of the sorbent pouch.

In any embodiment of the invention, it may be important to ensure thatthe sorbent pouches are properly inserted into the sorbent cartridge.Any method of doing so is contemplated by this invention. Onenon-limiting example is shown in FIG. 14 . Receiving groove 273 may becreated in the wall of the sorbent cartridge 272. A key 274, or flange,may be disposed on the side of the sorbent pouch 271. In order for thesorbent pouch 271 with key 274 to fit within the sorbent cartridge 272,the key 274 must be aligned with groove 273 in the sorbent cartridge 272wall. This will ensure that the sorbent pouch 271 is disposed within thesorbent cartridge 272 with the correct alignment. In any embodiment ofthe invention, optional ridges 275 may be placed within groove 273. Theridges 275 can serve to lock the sorbent pouch 271 in place verticallywithin the sorbent cartridge 272. The ridges 275 may be designed so thatthey are angled on the top portion of the ridge and flat on the bottomportion of the ridge. Once the key 274 passes a ridge 275 in a downwarddirection, the ridge 275 can serve to keep the sorbent pouch 271 frominadvertently moving back upward within the sorbent cartridge.

The ridges 275 may be designed such that the sorbent pouch 271 may beremoved upward only with the use of force greater than would be expectedfrom inadvertent moving but not so much force as to preventintentionally lifting the sorbent pouch 271 out of the sorbent cartridge272. This can be accomplished by using a semi-rigid material as eitherthe key 274, the ridges 275, or both, such that when enough force isapplied, the key 274 or ridges 275 can be bent far enough to allowremoval of the sorbent pouch 271, after which the key 274 or ridges 275can return to their original shape. In any embodiment of the invention,the ridges may be attached with a spring mechanism that is connected toa button, such that when the button is depressed the ridges 275 recedeinto the sorbent cartridge 272 and allow easy removal of the sorbentpouch 271.

In any embodiment of the invention, the sorbent pouches may be looselycontained within the sorbent cartridge. The sorbent pouch need not bemade the same size as, or larger than, the sorbent cartridge. One ormore sorbent pouches may be constructed of a smaller size than theinterior circumference of the sorbent cartridge, and may be simplyplaced in the sorbent cartridge.

After construction of the sorbent pouch containing a sorbent material ormaterials, the material within the sorbent pouch can be washed so as toremove any particles smaller than the pore or mesh size of the sorbentpouch material. This will ensure that all particles within the sorbentpouch are large enough so that they cannot inadvertently pass out of thesorbent pouch. Thus, when used in a sorbent cartridge, the sorbentpouches themselves can act as a particulate filter, ensuring that noparticulate matter of the sorbent material, or any other particulatematter, can pass downstream. This may eliminate the need for the use ofexternal particulate filters.

In any embodiment of the invention, antimicrobial or antibacterialmaterial may be impregnated into the sorbent pouch. This allowssterilization of the dialysate as the dialysate flows through thesorbent cartridge, and can eliminate the need for antimicrobial filters.In any embodiment of the invention, medication such as heparin or otheranticoagulants, or antibiotics may be impregnated into the sorbentpouch. This can allow administration of these medications to the patientwithout the need for adding the drugs to the dialysate.

In any embodiment of the invention, flow throughout the sorbent pouchcan be controlled by variations in the sorbent pouch material.Generally, fluid moving through a conduit will move most quickly throughthe center of the conduit, and more slowly towards the edges. To ensurethat fluid travels more evenly throughout the sorbent pouch, the sorbentpouch can be constructed such that more fluid enters the sorbent pouchon the outer edges of the sorbent pouch than enters in the center. Onenon-limiting example is shown in FIG. 15 . A sorbent pouch 281, such asone made out of a fabric, can be constructed with an extra layer offabric 282 in the center of the bottom surface of the sorbent pouch 281.This extra layer of fabric 282 effectively reduces the mesh size of thesorbent pouch 281 in that location. With a smaller mesh size, resistanceto flow will be greater in the center of the sorbent pouch 281, andfluid flow will be more evenly distributed to the edges of the sorbentpouch 281. In any embodiment of the invention where the sorbent pouch ismade out of metal or a polymer, the same effect can be created by makinga smaller pore size, or alternatively less pores, in the center of thesorbent pouch. In any embodiment of the invention, a separator, similarto the one shown in FIG. 11 can be utilized in the middle of the sorbentpouch. The separator can be constructed as described above, such as withan extra layer of fabric near the center, to better control the flow offluid throughout the sorbent pouch. Although shown in FIG. 15 as acentrally positioned rectangular layer, the extra layer of fabric 282 orother material may be positioned anywhere along the outer surface of thesorbent pouch 281, and may take any shape, such as circular,rectangular, triangular, etc.

In any embodiment of the invention, a patterned flow of fluid throughthe sorbent cartridge can be created. Occlusions, or blockages, of someof the pores can result in restricted flow through some portions of thesorbent pouch. In any embodiment of the invention, some of the pores inthe sorbent pouch may be larger or smaller than other pores in the restof the sorbent pouch. Flow will be increased through the larger pores ascompared to the smaller pores, allowing control over fluid flow into andout of the sorbent pouch.

Fluid flows through sorbent materials of varying particle sizes andgranular diameters at various rates and pressures. Fluid flows at ahigher rate and at a lower pressure through granules of larger diameter,while fluid flows at a slower rate and at a higher pressure throughgranules of smaller diameter. Wicking can occur when fluid generallyflows in the direction of areas of least pressure. For example, fluidflow through a fine particle sorbent material, such as zirconiumphosphate, can result in wicking. In such an instance, the fluid has atendency to flow towards an area of lower resistance, generally near thewall of the container. This can result in the fluid not flowing througha large portion of the sorbent material, such that the fluid is notcoming into contact with the sorbent materials. To ensure that fluidflows through the sorbent pouch and the sorbent materials more evenly,the sorbent pouches of the present invention can be constructed suchthat fluid is directed to flow away from the walls of the sorbent pouchand towards the interior of the sorbent pouch.

In any embodiment of the invention, flow of fluid through the sorbentpouches can be controlled by varying the interior diameters of thesorbent pouches. In FIG. 16 , the second sorbent pouch 102 has aninterior wall 105 that is thicker than the interior wall 104 of thefirst sorbent pouch 101, such that the interior diameter 109 of thesecond sorbent pouch 102 is smaller than the interior diameter 108 ofthe first sorbent pouch 101. Similarly, the third sorbent pouch 103 hasan interior wall 106 that is thicker than the interior wall 105 of thesecond sorbent pouch 102, such that the interior diameter 110 of thethird sorbent pouch 103 is smaller than the interior diameter 109 of thesecond sorbent pouch 102. Each sorbent pouch can have a wall that isthicker than that of the immediately preceding sorbent pouch in adirection from the bottom surface 120 of the first sorbent pouch 101 tothe top surface 170 of the third sorbent pouch 103 while maintaining asubstantially identical outer diameter among each sorbent pouch insequence. Any number of sorbent pouches can be used in any embodiment ofthis invention. Fluid flowing through the bottom surface 120 of thefirst sorbent pouch 101 to the top surface 130 of first sorbent pouch101, through the bottom surface 140 and top surface 150 of the secondsorbent pouch 102, and through the bottom surface 160 to the top surface170 of the third sorbent pouch 103, is directed into the interior spaceof each pouch. Because each sorbent pouch has a thicker wall than thepreceding sorbent pouch in series, each sorbent pouch has a smallereffective area through which fluid can flow than that of the precedingsorbent pouch. This gradually decreasing flow area will result inpushing the fluid moving from one sorbent pouch to another sorbent pouchalong the edges of the sorbent pouches near the wall of the sorbentcartridge 107 towards the center of the subsequent sorbent pouch. In anyembodiment of the invention, the wall of each sorbent pouch can bebetween 5-10% thicker than the wall of the preceding sorbent pouch. Inany embodiment of the invention, the thickness of the wall of eachsorbent pouch can be between 1-5%, 10-15%, 15-20% or 20-30% thicker thanthe wall of the preceding sorbent pouch.

FIG. 17 is an exploded perspective view of FIG. 16 . As can be seen,fluid flowing up through the first sorbent pouch 101 through sorbentpouches 102 and 103 will be pushed toward the center of each sorbentpouch by the thickening side walls of each sorbent pouch in series.

In any embodiment of the invention, each sorbent pouch may beconstructed with a smaller outside diameter than that of the precedingsorbent pouch. Constructing each sorbent pouch with a smaller diameterand the same wall thickness as the previous sorbent pouch will createthe same effect as constructing each sorbent pouch with a progressivelythicker wall. In any embodiment of the invention, as shown in FIG. 18 ,the interior diameter of the sorbent cartridge 124 can also decrease foreach sorbent pouch. The first sorbent pouch 121 can have the largestdiameter of all the sorbent pouches and can be placed in the sorbentcartridge 124 where the interior diameter of the sorbent cartridge 124is the largest. Second sorbent pouch 122 can have a smaller diameterthan that of the first sorbent pouch 121 and can be placed in thesorbent cartridge 124 where the interior diameter of the sorbentcartridge 124 is smaller. Third sorbent pouch 123 can have a smallerdiameter than that of the second sorbent pouch 122 and can be placed inthe sorbent cartridge 124 where the interior diameter of the sorbentcartridge 124 is smallest. The wall thickness 125 of each sorbentpouches can be constant. In any embodiment of the invention, more thanthree sorbent pouches can be used, and the sorbent cartridge 124 canhave more than three different sized interior diameters. In anyembodiment of the invention, fluid can flow up through bottom surface175 and top surface 180 of first sorbent pouch 121, through bottomsurface 185 and top surface 190 of second sorbent pouch 122, and throughbottom surface 195 and top surface 200 of third sorbent pouch 123 suchthat the fluid is passing through a constricting area with eachsubsequent sorbent pouch in series, and accordingly is pushed toward thecenter of each sorbent pouch.

In any embodiment of the invention, as shown in FIG. 19 , annular ringsor “o-rings” may be used to direct flow of fluid into the center of thesorbent pouch. A sorbent pouch 111 can have an annular ring 112 placedand adhered by any known means around the interior circumference of thesorbent pouch 111. The cross-section of the annular ring 112 can beangled so that the annular ring 112 extends radially into the interior113 of the sorbent pouch 111. The angle of the annular ring 112 candirect fluid entering the bottom surface 114 of the sorbent pouch 111from the area near the edge of the sorbent pouch 111 into the interior113 of the sorbent pouch 111 as the fluid exits through the top surface115 of the sorbent pouch 111. In any embodiment of the invention, theannular ring can have a curved shape. In any embodiment of theinvention, the annular ring can have a rectangular shape. In anyembodiment of the invention, each sorbent pouch can include multipleannular rings. For example, a sorbent pouch may have 2, 3, 4, 5, 6 ormore annular rings spaced along the interior circumference of thesorbent pouch to continuously push fluid into the center of the sorbentpouch as the fluid passes through the sorbent pouch. The annular ringsmay be made out of any substance known in the art. In any embodiment ofthe invention, the annular rings may be constructed from an elastomericmaterial, such as the o-rings described above. In any embodiment of theinvention, the annular rings may be constructed from plastic or someother inert material. In any embodiment of the invention, the annularrings may extend inwardly towards the center of the sorbent pouch at alength of between 5-10% of the diameter of the sorbent pouch. In anyembodiment of the invention, the annular rings may extend between 1-5%,10-15%, 15-20% or 20-30% of the diameter of the sorbent pouch.

One skilled in the art will understand that various combinations and/ormodifications and variations can be made in the stacked sorbent assemblydepending upon the specific needs for operation. Moreover, featuresillustrated or described as being part of the invention can be includedin the invention, either alone or in combination.

What is claimed is:
 1. A method, comprising the steps of: placing at least a first sorbent pouch in a sorbent cartridge; wherein the first sorbent pouch is formed from a porous material; wherein the first sorbent pouch contains urease and the porous material allows fluid to pass through the first sorbent pouch; wherein the porous material retains at least 98% by weight of solid urease in the first sorbent pouch; and wherein the porous material allows dissolved urease to pass through the first sorbent pouch.
 2. The method of claim 1, further comprising the step of placing at least a second sorbent pouch in the sorbent cartridge; wherein the second sorbent pouch contains alumina.
 3. The method of claim 2, further comprising the step of placing a third sorbent pouch in the sorbent cartridge; the second sorbent pouch containing at least one sorbent material selected from a group consisting of: activated carbon, zirconium phosphate, and zirconium oxide.
 4. The method of claim 2, further comprising the step of placing a third sorbent pouch in the sorbent cartridge; the second sorbent pouch containing zirconium phosphate.
 5. The method of claim 4, wherein the third sorbent pouch is placed downstream of the second sorbent pouch.
 6. The method of claim 1, wherein the first sorbent pouch further contains alumina.
 7. The method of claim 1, further comprising the step of placing a second sorbent pouch in the sorbent cartridge; the second sorbent pouch containing at least one sorbent material selected from a group consisting of: activated carbon, zirconium phosphate, and zirconium oxide.
 8. The method of claim 1, further comprising the step of placing a second sorbent pouch in the sorbent cartridge; the second sorbent pouch containing zirconium phosphate.
 9. The method of claim 6, wherein the second sorbent pouch is placed downstream of the first sorbent pouch.
 10. A method, comprising the steps of: flowing dialysate through a sorbent cartridge during a dialysis session; the sorbent cartridge comprising at least a first sorbent pouch; wherein the first sorbent pouch is formed from a porous material; wherein the first sorbent pouch contains urease; and wherein the porous material allows fluid to pass through the first sorbent pouch; wherein the porous material retains at least 98% by weight of solid urease in the first sorbent pouch; and wherein the porous material allows dissolved urease to pass through the first sorbent pouch.
 11. The method of claim 10, wherein the sorbent cartridge contains at least a second sorbent pouch; wherein the second sorbent pouch contains alumina.
 12. The method of claim 11, wherein the sorbent cartridge contains at least a third sorbent pouch; wherein the third sorbent pouch contains at least one sorbent material selected from a group consisting of: activated carbon, zirconium phosphate, and zirconium oxide.
 13. The method of claim 10, wherein the first sorbent pouch further contains alumina.
 14. The method of claim 10, wherein the sorbent cartridge contains at least a second sorbent pouch; the second sorbent pouch containing at least one sorbent material selected from a group consisting of: activated carbon, zirconium phosphate, and zirconium oxide.
 15. The method of claim 10, further comprising the step of measuring a concentration of at least one solute in a dialysate downstream of the sorbent cartridge.
 16. The method of claim 15, wherein the at least one solute comprises urea or ammonia. 